docs: def edge_val_set(self, graph, orig, dest, idx, key, branch, turn, tick, value):
          """Set this key of this edge to this value."""
          if (branch, turn, tick) in self._btts:
              raise TimeError
          self._btts.add((branch, turn, tick))
          graph, orig, dest, key, value = map(self.pack, (graph, orig, dest, key, value))
          self._edgevals2set.append(
              (graph, orig, dest, idx, key, branch, turn, tick, value)
          )